1. Field of the Invention
This invention relates to an image reader for optically reading original images.
2. Description of the Related Art
In image readers used for image scanners, facsimiles, copying machines, etc, it has become more and more popular to execute various image processings such as an image segmentation processing, an expansion/ reduction processing, a mirror inversion processing, a filter processing, a lightness/contrast correction processing, and so forth, for read image data, instead of using the image data as they are read out, and to utilize the image data after such image processings are executed.
As resolution of the image readers has become higher in recent years, however, the quantity of the data handled has become greater, and the problem has arisen in that the processing speed drops in those methods which process software-wise these image data.
To cope with this problem, a method has been employed which disposes an exclusive processing circuit dedicated to the image processing inside the image reader and accomplishes a high speed processing.
Hereinafter, an example of the conventional image readers will be explained with reference to the drawings.
FIG. 8 is a block diagram of the image reader according to the prior art.
A CCD (charge coupled device) image sensor 1 (hereinafter referred to as the "image sensor") photographs an object and outputs an image signal. An amplifier 2 amplifies the image signal outputted from the image sensor 1. An A/D converter 3 converts the image signal outputted from the amplifier 2 from an analog signal to a digital signal, and outputs the image signal as the digital image data. An image processing unit 4 executes image processings such as a shading processing, an MTF (modulation transfer function) correction, a main scanning direction magnification-changing processing, etc. A buffer memory 5 temporarily stores the image data. An interface unit 6 exchanges the image data with an external appliance (not shown). A timing generation circuit 7 controls the operations of the image sensor 1, the amplifier 2, the A/D converter 3, the image processing unit 4, the buffer memory 5 and the interface unit 6. A CPU (central processing unit) 8 controls the image reader as a whole. A ROM (read-only memory) 9 for CPU stores a control program for controlling the operation of the CPU 8. A RAM (random access memory) 10 is used as a work area of the CPU 8.
FIG. 9 is a block diagram showing the construction of the image processing unit 4 of the image reader shown in FIG. 8. As shown in FIG. 9, the image processing unit 4 comprises a shading processing unit 41, a main scanning direction magnification-changing processing unit 42, a moire removing processing unit 43, a mirror inversion processing unit 44, a segmentation processing unit 45, an MTF correction processing unit 46 and a binarization processing unit 47.
Next, the image processing function of the image reader shown in FIGS. 8 and 9 will be explained briefly.
To begin with, the shading processing unit 41 normalizes non-uniformity of illumination of a light source and variance of the sensitivity of the image sensor 1. The main scanning direction magnification-changing processing unit 42 executes enlargement/ reduction processing of the original image in a main scanning direction. The moire removing processing unit 43 reduces the influences of the moire resulting from the main scanning direction magnification-changing processing. The mirror inversion processing unit 44 outputs the image whose right and left sides are inverted to those of the original image. The segmentation processing unit 45 selects and outputs only a designated range with respect to the main scanning direction of the original image. The MTF correction processing unit 46 increases or decreases sharpness of the image. The binarization processing unit 47 converts multi-value image data to binary value data by a designated system such as simple binarization, dithering, an error diffusion processing, or the like. These image processing functions can be selectively turned ON and OFF on the basis of the data read mode designation from a host computer, etc.
To execute the image processing functions described above, at least one line of buffer memory is necessary for each function. In the image processing unit 4 shown in FIG. 9, a buffer memory 5 disposed for buffering the data input/output in the interface with the host computer serves also as the buffer memory for executing these image processings.
FIG. 10 is a block diagram showing another example of the construction of the image processing unit 4. In this structural example, dedicated memories 51 to 57 are disposed for the shading processing unit 41, the main scanning direction magnification-changing processing unit 42, the moire removing processing unit 43, the mirror inversion processing unit 44, the segmentation processing unit 45, the MTF correction processing unit 46 and the binarization processing unit 47, respectively, and in the image processing unit 4 shown in FIG. 10, too, the image processing functions similar to those of the image processing unit 4 shown in FIG. 9 are accomplished.
The buffer memory 5 of the image processing unit 4 shown in FIG. 9 is originally disposed so as to play the role of a buffer in the interface with the host computer, and the buffer memory necessary for executing each image processing of each of the processing units ranging from the shading processing unit 41 to the binarization processing unit 47 is executed also by this buffer memory 5. In consequence, the number (capacity) of the memories can be minimized, and an economical image reader can be acquired.
However, because the access to the buffer memory 5 frequently occurs, a problem exists in that the processing quantity of the data per unit time (output throughput) drops significantly.
In the image processing unit 4 shown in FIG. 10, on the other hand, the dedicated memories 51 to 57 are disposed for the processing units 41 to 47, respectively. Therefore, output through-put of the data can be increased, it is true, but another problem occurs that the memory cost increases.
It is therefore an object of the present invention to provide an image reader which can execute a plurality of image processings by a smaller memory capacity but has a high data output through-put.
An image reader according to the present invention includes storage means for storing original image data to be read and read means for reading out the original image data stored in the storage means in accordance with a designated magnification-changing ratio and with a segmentation area.
Because the original image data stored in the storage means are read out in accordance with the magnification ratio and with the segmentation area, the magnification-changing processing and segmentation processing of the original image data can be collectively carried out. Therefore, the present invention can provide an image reader capable of executing a plurality of image processings by a smaller memory capacity and having a high data output through-put.